Phase-change materials (PCMs) can be implemented into building practice to enhance thermal storage performance, reduce indoor temperature fluctuations, and improve the thermal comfort of occupants. As building energy simulation is taking an ever larger role in the design and analysis of energyefficient buildings, it is important to understand the capabilities and performance of these tools. A popular and powerful building simulation program is ESP-r, which is capable of incorporating the use of PCMs into the thermal simulation. An effect of using multiple layers of PCMs versus using a single layer was investigated using the BESTEST standard (ASHRAE 2004). It was found that in general, the application of PCMscan significantly affect the thermal performance of the building.